When your program blocks, hit control-\ and you'll get a stack trace of
every running goroutine, the ones blocked inside downPart will point to the
place they are blocked.
On Sunday, 15 January 2017 05:33:25 UTC+11, vyasgir...@gmail.com wrote:
>
> I am implementing a multi part file downloader and I need help to find the
> blocking element in the following piece of code.
>
>
> func downPart(wg *sync.WaitGroup, url string, dataChan chan []byte, range1
> , range2 int) {
>
>
> defer wg.Done()
> client := new(http.Client)
> req, _ := http.NewRequest("GET", url, nil)
>
>
> req.Header.Set("Range", strconv.Itoa(range1)+"-"+strconv.Itoa(range2))
> data, err := client.Do(req)
> if err != nil {
> fmt.Println(err)
> return
> }
> dataByte := new(bytes.Buffer)
> dataByte.ReadFrom(data.Body)
> fmt.Println("Done")
>
>
> dataChan <- dataByte.Bytes()
> }
> func multiDownload(url string, length int) bool {
> var wg sync.WaitGroup
>
>
> x := 4
> split := length / x
> fmt.Println(length)
> dataChan := make([]chan []byte, x)
> for i := 0; i < x; i++ {
> wg.Add(1)
>
>
> range1 := i * split
> range2 := (i+1)*split - 1
> if range2 == length-2 {
> range2 = length
> }
> fmt.Println(len(dataChan), range1, range2)
> go downPart(&wg, url, dataChan[i], range1, range2)
> }
>
>
> var data []byte
> wg.Wait()
>
>
> for i := 0; i < x; i++ {
> fmt.Println("waiting")
> data = <-dataChan[i]
> fmt.Println(data)
> }
> return true
>
> }
>
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